Oscillating chemical mechanical planarization apparatus

ABSTRACT

A chemical mechanical polishing (CMP) apparatus is provided. The CMP apparatus includes a first roller situated at a first point and a second roller situated at a second point. The first point is separate from the second point. Also included in the apparatus is a polishing pad strip having a first end secured to the first roller and a second end secured to the second roller. The first roller and the second roller are configured to reciprocate so that the polishing pad strip oscillates at least partially between the first point and the second point.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This Application is a continuation of application Ser. No.09/608,513, filed Jun. 30, 2000, from which priority under 35 U.S.C.§120 is claimed. The disclosure of this Application is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to chemical mechanicalpolishing (CMP) systems and techniques for improving the performance andeffectiveness of CMP operations. Specifically, the present inventionrelates to CMP systems that use a fixed abrasive polishing pad arrangedin a web handling system.

[0004] 2. Description of the Related Art

[0005] In the fabrication of semiconductor devices, there is a need toperform CMP operations, including polishing, buffing and wafer cleaning.Typically, integrated circuit devices are in the form of multi-levelstructures. At the substrate level, transistor devices having diffusionregions are formed. In subsequent levels, interconnect metallizationlines are patterned and electrically connected to the transistor devicesto define the desired functional device. As is well known, patternedconductive layers are insulated from other conductive layers bydielectric materials, such as silicon dioxide. As more metallizationlevels and associated dielectric layers are formed, the need toplanarize the dielectric material increases. Without planarization,fabrication of additional metallization layers becomes substantiallymore difficult due to the higher variations in the surface topography.In other applications, metallization line patterns are formed in thedielectric material, and then metal CMP operations are performed toremove excess metallization.

[0006] In the prior art, CMP systems typically implement belt, orbital,or brush stations in which belts, pads, or brushes are used to scrub,buff, and polish one or both sides of a wafer. Slurry is used tofacilitate and enhance the CMP operation. Slurry is most usuallyintroduced onto a moving preparation surface, e.g., belt, pad, brush,and the like, and distributed over the preparation surface as well asthe surface of the semiconductor wafer being buffed, polished, orotherwise prepared by the CMP process. The distribution is generallyaccomplished by a combination of the movement of the preparationsurface, the movement of the semiconductor wafer and the frictioncreated between the semiconductor wafer and the preparation surface.

[0007]FIG. 1 illustrates an exemplary prior art CMP system 100. The CMPsystem 100 in FIG. 1 is a belt-type system, so designated because thepreparation surface is an endless belt 108 mounted on two drums 114which drive the belt 108 in a rotational motion as indicated by beltrotation directional arrows 116. A wafer 102 is mounted on a carrier104. The carrier 104 is rotated in direction 106. The rotating wafer 102is then applied against the rotating belt 108 with a force F toaccomplish a CMP process. Some CMP processes require significant force Fto be applied. A platen 112 is provided to stabilize the belt 108 and toprovide a solid surface onto which to apply the wafer 102. Slurry 118composing of an aqueous solution such as NH₄OH or DI water containingdispersed abrasive particles is introduced upstream of the wafer 102.The process of scrubbing, buffing and polishing of the surface of thewafer is achieved by using an endless polishing pad glued to the belt108. Typically, the polishing pad is composed of porous or fibrousmaterials and lacks fixed abrasive particles.

[0008] After the polishing pad polishes a limited number of wafers, thesurface of the pad is conditioned and cleaned in order to remove theattached abrasive materials of the slurry and the particles removed fromthe wafer. Subsequent to cleaning and conditioning, the polishing padwill have a significant amount of particles that remain attached to thesurface of the polishing pad causing the polishing pad to lose itseffectiveness. The polishing pad also loses its effectiveness due tonormal wear of the material itself. As a result, the polishing pad mustbe replaced in its entirety. The removal of the used polishing pad andits subsequent replacement with a new polishing pad is very timeconsuming and labor intensive. Additionally, the time needed to performthe replacement necessarily requires that the polishing system be takenoff-line, which thus reduces throughput.

[0009] In view of the foregoing, a need therefore exists in the art fora chemical mechanical polishing system that will enable polishingsurface layers of a wafer using a polishing pad that is less expensiveto maintain and is more effectively serviced after its use degrades theeffectiveness of the polishing.

SUMMARY OF THE INVENTION

[0010] Broadly speaking, the present invention fills these needs byproviding an apparatus and related methods for efficiently polishinglayer surfaces of a semiconductor wafer. Preferably, the CMP system isdesigned to implement a polishing pad strip that is less expensive tomaintain and is more efficiently serviced after it loses itseffectiveness to polish. In preferred embodiments, the polishing pad isa fixed abrasive polishing pad strip that is connected between a feedroll and a take-up. It should be appreciated that the present inventioncan be implemented in numerous ways, including as a process, anapparatus, a system, a device, or a method. Several inventiveembodiments of the present invention are described below.

[0011] In one embodiment, a chemical mechanical polishing (CMP)apparatus is provided. The CMP apparatus includes a polishing pad strip,a feed roll, and a take-up roll. The polishing pad strip is definedbetween a first point and a second point wherein the first point isseparate from the second point. The feed roll defines the first pointand has a supply of the polishing pad strip. The take-up roll definesthe second point and is configured to collect at least a linear portionof the polishing pad strip. The feed roll and the take-up roll areconfigured to reciprocate so that the polishing pad strip oscillates atleast partially between the first point and the second point.

[0012] In another embodiment, a chemical mechanical polishing (CMP)apparatus is provided. The CMP apparatus includes a polishing pad stripdefined between a first point and a second point wherein the first pointbeing separate from the second point. A feed roll that defines the firstpoint and has a supply of the polishing pad strip. A take-up roll thatdefines the second point and collects at least a linear portion of thepolishing pad strip. The feed roll and the take-up roll are configuredto reciprocate so that the polishing pad strip oscillates at leastpartially between the first point and the second point at a programmablerate at least partially between the first point and the second point.The programmable rate defines a linear velocity for the polishing padstrip in a direction between the first point and the second point aswell as between the second point and the first point.

[0013] In still a further embodiment, a chemical mechanical polishing(CMP) apparatus is provided. The CMP apparatus includes a first rollersituated at a first point and a second roller situated at a secondpoint. The first point is separate from the second point. Also includedin the apparatus is a polishing pad strip having a first end secured tothe first roller and a second end secured to the second roller. Thefirst roller and the second roller are configured to reciprocate so thatthe polishing pad strip oscillates at least partially between the firstpoint and the second point.

[0014] The advantages of the present invention are numerous. Mostnotably, instead of a continuous belt polishing pad, a supply ofpolishing pad strip is provided between a feed roll and a take-up rollin a web handling arrangement. Thus, replacing used portions of thepolishing pad strip with fresh portions of the polishing pad strip canbe accomplished utilizing minimal effort and in significantly lessamount of time. Furthermore, the re-supplying of the polishing pad stripcan be achieved easily and expeditiously thereby minimizing the lengthof time needed to take the polishing system off-line thus having minimaleffect on the throughput. Accordingly, the apparatus and the methods ofthe present invention provide for polishing surface layers of a waferusing a polishing pad that is less expensive to maintain and is moreeffectively serviced after its use degrades the effectiveness of thepolishing.

[0015] Other aspects and advantages of the invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, illustrating by way of example theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings, andlike reference numerals designate like structural elements.

[0017]FIG. 1 illustrates an exemplary prior art CMP system.

[0018]FIG. 2A is a cross-sectional view of an oscillating CMP system, inaccordance with one embodiment of the present invention.

[0019]FIG. 2B is a cross-sectional view of an oscillating CMP system,illustrating the system's tension setting mechanism and velocity controlmechanism, in accordance with another embodiment of the presentinvention.

[0020]FIG. 2C is a cross-sectional view of an oscillating CMP system,illustrating the feed roll's design to hold an ample supply of thepolishing pad strip, in accordance with yet another embodiment of thepresent invention.

[0021] FIGS. 2D-1 is a plan-view of an abrasive polishing pad strip, inaccordance with yet another embodiment of the present invention.

[0022] FIGS. 2D-2 is a cross-sectional view of an abrasive polishing padstrip, revealing the plurality of posts containing a plurality ofabrasive particles, in accordance with yet another embodiment of thepresent invention.

[0023]FIG. 3A is a cross-sectional view of the CMP system in which thetension actuators are positioned to the right and to the left of thefeed roll and the take-up roll, respectively, in accordance with yetanother embodiment of the present invention.

[0024]FIG. 3B is a cross-sectional view of the CMP system, depicting thesystem's tension setting and velocity control mechanisms, in accordancewith yet another embodiment of the invention.

[0025]FIG. 4A is a cross-sectional view of the CMP system in which thetension actuators are connected to the idler rollers, in accordance withyet another embodiment of the present invention.

[0026]FIG. 4B is a cross-sectional view of the CMP system, depicting thesystem's tension setting mechanism as well as velocity controlmechanism, in accordance with yet another embodiment of the invention.

[0027]FIG. 5A is a cross-sectional view of the CMP system in which thefeed roll and take-up roll maintain and control both the tension exertedon the polishing pad strip as well as the linear velocity of thepolishing pad strip, in accordance with yet another embodiment of theinvention.

[0028]FIG. 5B is a cross-sectional view of the CMP system, depicting thesystem's tension and velocity control mechanism, in accordance with yetanother embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] An invention for a CMP system, which enables efficient polishingof layer surfaces of a wafer is described. The CMP system preferablyimplements a polishing pad that is less expensive to maintain and ismore efficiently serviced after it loses its effectiveness to polish. Inpreferred embodiments, the polishing pad is a fixed abrasive polishingpad. The fixed abrasive polishing pad is preferably provided as apolishing pad strip that is connected between a feed roll and a take-up.This configuration is referred to herein as a web handling arrangement.In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be understood, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

[0030]FIG. 2A is a cross-sectional view of an oscillating CMP system200, in accordance with one embodiment of the present invention. The CMPsystem 200 in FIG. 2A includes a feed roll 212 a positioned at a firstpoint 211 a. The feed roll 212 a is configured to hold a roll of apolishing pad strip 202. A take-up roll 212 b is positioned at a secondpoint 211 b, and is placed, in this embodiment, symmetrically acrossfrom the feed roll 212 a and is configured to receive the polishing padstrip 202. The direct distance between the feed roll 212 a and take-uproll 212 b is estimated to be about 20 inches. Of course, the distancebetween the feed roll 212 a and take-up roll 212 b may vary depending onthe specific implementation. In this embodiment, each of the feed roll212 a and the take-up roll 212 b is designed to contain an internalmotor. Preferably, the internal motor is a servo drive, such as a directdrive servo. The internal motors are designed to allow the feed roll 212a and take-up roll 212 b to reciprocate. The reciprocating motions ofthe feed roll 212 a and take-up roll 212 b cause the polishing pad stripto oscillate at a linear velocity ranging from about 140 feet per secondto about 350 feet per second. The actual linear velocity selected for apolishing operation will also depend on the force at which a polishinghead holding a wafer is applied to the polishing pad strip and theplaten. The limits of the linear velocity and the force are generallycalibrated using the well known Preston's Equation. According toPreston's Equation, Removal Rate=KpPV, where the removal rate ofmaterial is a function of Downforce (P) and Linear Velocity (y), with Kpbeing the Preston Coefficient, a constant determined by the chemicalcomposition of the slurry (or fixed abrasive material and chemicals),the process temperature, and the pad surface, among other variables.

[0031] In this embodiment, tension actuators 214 a and 214 b arepositioned directly below the feed roll 212 a and take-up roll 212 b,respectively. The tension actuators 214 a and 214 b are configured tocontrollably pull on the feed roll 212 a and take-up roll 212 b therebycausing the feed roll 212 a and take-up roll 212 b to exert tension onthe polishing pad strip 202. It should be understood that each of thetension actuators can be any type of linear actuator. For instance, eachtension actuator can be replaced with cylinders, coils, screws or linearmotors.

[0032] Positioned above the feed roll 212 a is a load cell roller 208 adefined by a roller that measures the tension exerted on the polishingpad strip 202 on the side closest to intermediate point 207 a (e.g.,left side). The load cell roller 208 b is also defined by a roller thatmeasures the tension exerted on the polishing pad strip 202 on the sideclosest to the intermediate point 207 b (e.g., right side). In thisexample, the load cell roller 208 b is positioned symmetrically acrossfrom the load cell roller 208 a and directly above the take-up roll 211b. Therefore, the polishing pad strip 202 is located on top of the loadcell rollers 208 a and 208 b, and the load cell rollers 208 a and 208 bare configured to provide a location where the polishing pad strip 202is caused to change angular orientation. For instance, the angularorientation may be about 90 degrees so that only the horizontalcomponents of the forces applied on the load cell rollers 208 a and 208b are measured. An idler roller 210 a defined by a roller fixed to apoint is positioned between feed roll 212 a and load cell roller 208 a.Across from the idler roller 210 a, is positioned an idler roller 210 b.The idler rollers 210 a and 210 b are designed to support the polishingpad strip along a path that will ensure the 90-degree angle describedabove. Thus, the idler rollers 210 a and 210 b are further designed toallow the load cell rollers 208 a and 208 b to measure only thehorizontal components of the forces applied on the load cell rollers 208a and 208 b. The horizontal components of the applied forces areequivalent to the tension exerted on the polishing pad strip 202 on theleft side and the right side of the polishing head 204.

[0033] A polishing head 204 is designed to carry a wafer (not shown inthe figure) and rotates in a rotation direction 205. A platen 206 ispositioned horizontally between load cell rollers 208 a and 208 b.Platen 206 is configured to stabilize the polishing pad strip 202 and toprovide a solid surface onto which to apply the polishing head 204. Insome cases, it is possible to control the surface between the platen 206and the polishing pad strip 202 to control the removal rate in differentlocations on the wafer. In one embodiment, the polishing pad strip 202is a fixed abrasive polishing pad, which has a polishing layercontaining abrasive particles extended throughout the surface and thematerial thickness. As the polishing head 204 applies the wafer (notshown in the figure) against the polishing pad strip 202, the abrasiveparticles of the polishing pad strip 202 become loose therebyeliminating the necessity to use a slurry containing abrasive materials.Although a slurry containing abrasive particles is not required, aliquid solution (e.g., NH₄OH or DI water) is preferably used tofacilitate the polishing process.

[0034] As depicted in the embodiment of FIG. 2B, a certain portion ofthe supplied polishing pad strip 202 held in the feed roll 212 a is fedaround the load cell rollers 208 a and 208 b to the take-up roll 211 b.After polishing a given number of wafers, the portion of the polishingpad strip 202 which came into contact with the wafers loses itseffectiveness and must be replaced. The used portion of the polishingpad strip 202 is replaced by an unused portion of the polishing padstrip 202 by way of the feed roll 212 a indexing the polishing pad strip202, utilizing a programmable amount (e.g., enough to place a freshportion of the polishing pad strip 202 over the platen 206). Theindexing causes the used portions of the polishing pad strip 202 to bepushed farther and farther away from the polishing area. The usedportions of the polishing pad strip 202 are collected by the take-uproll 212 b and will ultimately be discarded. Once the supply of thepolishing pad strip 202 held in feed roll 212 a is completely consumed,it can easily be replaced with a new roll of the polishing pad strip202. The process of re-supplying the feed roll 212 a with the polishingpad strip 202 is neither labor intensive nor time consuming. Moreimportantly, the CMP machine will be off-line, if necessary, lessfrequently and for a significantly less amount of time thereby causingminimal effect on the throughput of the machine.

[0035] Also clearly shown in FIG. 2B are the tension actuators 214 a and214 b which are configured to controllably pull on the feed roll 212 aand take-up roll 212 b causing the feed roll 212 a and take-up roll 212b to apply pressure to the polishing pad strip 202 at the firstintermediate point 207 a and the second intermediate point 207 b,respectively. Due to normal wear, the polishing pad strip 202 canstretch, thereby causing the amount of tension exerted on the polishingpad strip 202 to reduce. This system is designed to maintain a desiredtension by way of changing the amount of force the tension actuators 214a and 214 b apply on the feed roll 212 a and take-up roll 212 b,respectively.

[0036] This task is achieved by the load cell roller 208 a sending atension feedback signal to an amplifier 222 a, which is a part of afirst tension-velocity controller 220 a. Subsequently, a tension settingcommand, either supplied manually or automatically through acomputerized device, is fed to the amplifier 222 a. Thereafter, theamplifier 222 a sends a tension output signal to a tension controldevice 226 a, which is also a part of the tension-velocity controller220 a. Finally, the tension control device 226 a sends a tension (TN)signal to the tension actuator 214 a.

[0037] In a like manner, an amplifier 222 b, which is a part of atension-velocity controller 220 b receives a tension feedback (FB)signal from load cell roller 208 b. Subsequently, a tension settingcommand, either supplied manually or automatically through acomputerized device, is fed to the amplifier 222 b. Thereafter, theamplifier 222 b sends a tension (TN) output signal to a tension controldevice 226 b, which is also a part of the tension-velocity controller220 b. Finally, the tension control device 226 b sends a tension signalto the tension actuator 214 a. Depending on the tension signals receivedfrom the tension-velocity controllers 220 a and 220 b, the tensionactuators 214 a and 214 b may or may not exert additional force on thefeed roll 212 a and take-up roll 212 b so as to achieve a desiredtension (e.g., either higher or lower).

[0038] Once the desired tension is exerted on the polishing pad strip202, the internal motors located inside the feed roll 212 a and take-uproll 212 b will cause the feed roll 212 a and take-up roll 212 b toreciprocate, synchronously, thereby causing the polishing pad strip 202to oscillate at a linear velocity. In one embodiment, to achieve optimumperformance, the linear velocity of the polishing pad strip 202 shouldbe maintained within the range of about 140 ft/sec and about 350 ft/sec.Thus, the linear velocity of the polishing pad strip 202 should bemeasured frequently by the feed roll 212 a and take-up roll 212 b.Besides measuring the velocity of the polishing pad strip 202, the feedroll 212 a and take-up roll 212 b control and change, if necessary, thevelocity of the polishing pad 202 so as to maintain a desired velocity.

[0039] As an example, the feed roll 212 a initially sends out a velocityfeedback to a Proportional, Integral and Derivative (PID) 224 a, whichis a part of the tension-velocity controller 220 a. Then, a velocitysetting command, either supplied manually or automatically using acomputerized device, is fed to the PID 224 a. Finally, the PID 224 asends out a velocity signal to the feed roll 212 a.

[0040] Similarly, the take-up roll 212 b sends out a velocity feedbackto a Proportional, Integral and Derivative (PID) 224 b, which is a partof the tension-velocity controller 220 b. Then, a velocity settingcommand, either supplied manually or by way of a programmable machine,is fed to the PID 224 b. Finally, the PID 224 b sends out a velocitysignal to the take-up roll 212 b. The velocity signals received by thefeed roll 212 a and the take-up roll 212 b are the determinative factorsas to whether the feed roll 212 a and take-up roll 212 b must maintainor change the rate of reciprocating. Although the tension-velocitycontrollers 220 a and 220 b have been illustrated using exemplaryelectronics, it should be understood that the electronics and controlsignals can be processed using any other suitable well known processingtechniques (e.g., software/hardware combinations). For instance, the PIDelectronics can be substituted with other circuitry that can process andcontrol the signals as may be desired.

[0041] As clearly evident from the embodiment of FIG. 2C, the feed roll212 a is designed to hold an ample supply of the polishing pad strip202. Utilizing minimal effort, the feed roll 212 a can be re-suppliedwith the fresh polishing pad strip 202 thereby having minimum effect onthe throughput of the CMP machine.

[0042] FIGS. 2D-1 depicts one of many types of the polishing pad strip202, which has a fixed abrasive polishing layer. The approximatethickness of this type of polishing pad strip 202 ranges from about0.004 inch to about 0.010 inch. Embedded and extended through out thesurface of this type of polishing pad strip 202 are severalthree-dimensional protrusions, which are defined as posts 202′. Thecross-sectional view of the polishing pad strip 202, as shown in FIGS.2D-2, reveals that each post 202′ contains a plurality of abrasiveparticles having an approximate size in the range from about 40micrometer and about 200 micrometer.

[0043] Another embodiment of the present invention is shown in FIG. 3Awherein the tension actuator 314 a is positioned to the right of thefeed roll 212 a. In a like manner, the tension actuator 314 b issituated to the left of the take-up roll 212 b. In this embodiment, byrespectively pulling on the feed roll 212 a and take-up roll 212 b, thetension actuators 314 a and 314 b will cause the feed roll 212 a andtake-up roll 212 b to controllably exert tension on the polishing padstrip 202.

[0044] For example, in the embodiment of FIG. 3B, the tension actuators314 a and 314 b control the amount of tension exerted on the polishingpad strip 202. This is achieved by the load cell roller 208 a sendingout a tension feedback to the tension/velocity controller 220 a, whichin turn, after internally processing the tension feedback, sends atension signal to the tension actuator 314 a. Similarly, the load cellroller 208 b sends out a tension feedback to the tension/velocitycontroller 220 b. Once the tension/velocity controller 220 b processesthe tension feedback, internally, it sends a tension signal to thetension actuator 314 b. Depending on the tension signals received, ifnecessary, the tension actuators 314 a and 314 b, may change the amountof force each of them exerts on the feed roll 212 a and take-up roll 212b so as to achieve a desired tension.

[0045] Once the desired tension is set for the polishing pad strip 202,the synchronous reciprocation of the feed roll 212 a and take-up roll212 b start thereby causing the polishing pad strip 202 to oscillate ata linear velocity. In one embodiment, the linear velocity of thepolishing pad strip 202 may be measured frequently or at set times.Depending upon the measurements, adjustments can be made to the tensionthat is controlled by the feed roll 212 a and take-up roll 212 b. Thefeed roll 212 a and take-up roll 212 b each send out a velocity feedbackto the tension/velocity controllers 220 a and 220 b, respectively. Then,after internally processing the velocity feedbacks, the tension/velocitycontrollers 220 a and 220 b, each sends out a velocity signal to thefeed roll 212 a and take-up roll 212 b. Depending on the velocitysignals received, if necessary, the feed roll 212 a and take-up roll 212b may change the rate of reciprocating, thus fixing a new linearvelocity for the polishing pad strip 202.

[0046] The embodiment of FIG. 4A depicts an oscillating CMP system 200 bthat is similar to the embodiment of FIG. 2A, with the exception thatthe tension actuators 414 a and 414 b are positioned outside the idlerrollers 210 a and 210 b. In this embodiment, the tension actuators areconfigured to pull on the idler rollers 210 a and 210 b so as to causethe idler rollers 210 a and 210 b to exert tension on the polishing padstrip 202.

[0047] In this case, there will be points in time when the verticalportions of the polishing pad strip 202 will not be at a 90 degree anglerelative to the polishing region (e.g., where the platen 206 is located)of the polishing pad strip 202. Nevertheless, the tension can becontrollably adjusted to a correct desired level. It should therefore beunderstood that it is not necessary to have the vertical and horizontalportions of the polishing pad strip 202 at a 90 degree angle at alltimes so long as the polishing pad strip 202 provides the desiredoptimum polishing condition at the location where polishing is to beperformed on the wafer surfaces.

[0048] As shown in the embodiment of FIG. 4B, the load cell roller 208 asends out a tension feedback to the tension/velocity controller 220 a.After internally processing the tension feedback, the tension/velocitycontroller 220 a sends out a tension signal to the tension actuator 414a. Similar signals are also exchanged between the load cell roller 208b, tension/velocity controller 220 b and tension actuator 414 b.

[0049] Once each of the tension actuators 414 a and 414 b respectivelyreceive a tension signal from 220 a and 220 b, depending on the tensionsignals received, tension actuators may, if necessary, change the forceby which they exert tension on the polishing pad strip 202. Afterachieving the desired tension, the feed roll 212 a and take-up roll 212b start reciprocating, preferably synchronously, causing the polishingpad strip to oscillate at a desired linear velocity. Similar to theembodiments of FIGS. 2B and 3B, the feed roll 212 a and take-up roll 212b maintain and if necessary, change the velocity of the oscillation ofthe polishing pad strip 202.

[0050]FIG. 5A depicts an oscillating CMP system 200 c wherein the feedroll 212 a and take-up roll 212 b maintain and control both the tensionexerted on the polishing pad strip 202 as well as the linear velocity ofthe polishing pad 202. Accordingly, the tension actuators havecompletely been eliminated from the CMP system 200 c.

[0051] As illustrated in FIG. 5B, in a CMP system 200 c′, the load cellroller 208 a sends a tension feedback to an amplifier 322 a that is partof the tension-and-velocity controller 320 a. Thereafter, a tensionsetting command, supplied either manually or automatically through acomputerized device, is fed to the amplifier 322 a. Then, the amplifier322 a sends a tension output signal to a tension and velocity controldevice 326 a.

[0052] Thereafter, a velocity feedback is sent from feed roll 212 a to aPID 324 a also positioned within the tension-and-velocity controller 320a. In a subsequent operation, a velocity setting command, suppliedeither manually or by way of a programmable machine, is fed to the PID324 a. Then, the PID 324 a sends a velocity output signal to the tensionand velocity control 326 a. After receiving the tension output signaland the velocity output signal, the tension and velocity control 326 asends out a tension and velocity signal to the feed roll 212 a.

[0053] Similarly, a tension feedback and a velocity feedback arerespectively fed to an amplifier 322 b and a PID 324 b, which are partof the tension-and-velocity controller 320 b. Then, a tension settingcommand is fed to the amplifier 322 b, which in turn, sends out atension output signal to a tension and velocity control 326 b, which isalso a part of the tension-and-velocity controller 320 b. Next, avelocity setting command is fed to the PID 324 b, which subsequentlysends out a velocity command signal to the tension and velocity control326 b. After receiving the tension output signal and the velocity outputsignal, the tension and velocity control 326 b sends out a tension andvelocity signal to the take-up roll 212 b.

[0054] Depending on the tension and velocity signals received by thefeed roll 212 a and take-up roll 212 b, the feed roll 212 a and take-uproll 212 b may, if necessary, each rotate inwardly in the direction (TA)so as to adjust the tension exerted on the polishing pad strip 202 to adesired level. Once the tension applied to the polishing pad strip 202is set to a desired level, the feed roll 212 a and take-up roll 212 bstart, preferably, a synchronous reciprocation thereby causing thepolishing pad to oscillate at a linear velocity under the polishing head204. Thus, in this embodiment, similar to some of the embodiments, thefeed roll 212 a and take-up roll 212 b can change, if necessary, thevelocity of the polishing pad 202 so as to maintain a desired velocityfor optimum polishing performance.

[0055] Although the foregoing invention has been described in somedetail for purposes of clarity of understanding, it will be apparentthat certain changes and modifications may be practiced within the scopeof the appended claims. For example, embodiments described herein havebeen primarily directed toward wafer polishing, however, it should beunderstood that the polishing operations are well suited for precisionpolishing of any type of substrate. Accordingly, the present embodimentsare to be considered as illustrative and not restrictive, and theinvention is not to be limited to the details given herein, but may bemodified within the scope and equivalents of the appended claims.

What is claimed is:
 1. A chemical mechanical polishing (CMP) apparatus,comprising: a polishing pad strip defined between a first point and asecond point, the first point being separate from the second point; afeed roll having a supply of the polishing pad strip, and the feed rolldefining the first point; and a take-up roll configured to collect atleast a linear portion of the polishing pad strip, the take-up rolldefining the second point, wherein the feed roll and the take-up rollare configured to reciprocate so that the polishing pad strip oscillatesat least partially between the first point and the second point.
 2. Achemical mechanical polishing (CMP) apparatus as recited in claim 1,wherein the polishing pad strip oscillates at a programmable rate atleast partially between the first point and the second point.
 3. Achemical mechanical polishing (CMP) apparatus as recited in claim 2,wherein the programmable rate defines a linear velocity for thepolishing pad strip in a direction between the first point and thesecond point as well as between the second point and the first point. 4.A chemical mechanical polishing (CMP) apparatus as recited in claim 1,further comprising: a first tension actuator connected to the feed roll;and a second tension actuator connected to the take-up roll, wherein thefirst tension actuator is configured to controllably pull on the feedroll so as to apply tension to the polishing pad strip, and wherein thesecond tension actuator is configured to controllably pull on thetake-up roll so as to apply tension to the polishing pad strip.
 5. Achemical mechanical polishing (CMP) apparatus as recited in claim 4,further comprising: a first load cell roller; and a second load cellroller, the first load cell roller being defined at a first intermediatepoint and the second load cell roller being defined at a secondintermediate point, the first intermediate point and the secondintermediate point being located under and supporting the polishing padstrip and between the first point and the second point.
 6. A chemicalmechanical polishing (CMP) apparatus as recited in claim 5, furthercomprising: a first idler roller positioned between the first point andthe first intermediate point, the first idler roller configured tomaintain a constant positional velocity for the polishing pad strip at atangential interface with the first intermediate point defined by thefirst load cell roller; and a second idler roller positioned between thesecond point and the second intermediate point, the second idler rollerconfigured to maintain a constant positional velocity for the polishingpad at a tangential interface with the second intermediate point definedby the second load cell roller.
 7. A chemical mechanical polishing (CMP)apparatus as recited in claim 5, further comprising: a firsttension-velocity controller; and a second tension-velocity controller,each of the first and second tension-velocity controller beingconfigured to receive a tension feedback signal, a tension settingcommand, a velocity feedback signal, and a velocity setting command, andeach of the first and second tension-velocity controller beingconfigured to output a velocity setting signal and a tension settingsignal.
 8. A chemical mechanical polishing (CMP) apparatus, comprising:a polishing pad strip defined between a first point and a second point,the first point being separate from the second point; a feed roll havinga supply of the polishing pad strip, and the feed roll defining thefirst point; and a take-up roll configured to collect at least a linearportion of the polishing pad strip, the take-up roll defining the secondpoint, wherein the feed roll and the take-up roll are configured toreciprocate so that the polishing pad strip oscillates at leastpartially between the first point and the second point at a programmablerate at least partially between the first point and the second point,and wherein the programmable rate defines a linear velocity for thepolishing pad strip in a direction between the first point and thesecond point as well as between the second point and the first point. 9.A chemical mechanical polishing (CMP) apparatus as recited in claim 8,further comprising: a first tension-and-velocity controller; and asecond tension-and-velocity controller, each of the first and secondtension-and-velocity controller being configured to receive a tensionfeedback signal, a tension setting command, a velocity feedback signal,and a velocity setting command, and each of the first and secondtension-and-velocity controller being configured to output atension-and-velocity setting signal.
 10. A chemical mechanical polishing(CMP) apparatus as recited in claim 8, wherein each of the first andsecond tension-and-velocity controller includes a tension and velocitycontrol for setting each of the feed roll and the take-up roll,respectively.
 11. A chemical mechanical polishing (CMP) apparatus asrecited in claim 8, further comprising: a first load cell roller; asecond load cell roller, the first load cell roller being defined at afirst intermediate point and the second load cell roller being definedat a second intermediate point, the first intermediate point and thesecond intermediate point being located under and supporting thepolishing pad strip and between the first point and the second point; afirst idler roller positioned between the first point and the firstintermediate point; and a second idler roller positioned between thesecond point and the second intermediate point.
 12. A chemicalmechanical polishing (CMP) apparatus as recited in claim 11, furthercomprising: a first tension actuator connected to the first idlerroller; and a second tension actuator connected to the second idlerroller.
 13. A chemical mechanical polishing (CMP) apparatus, comprising:a first roller situated at a first point and a second roller situated ata second point, the first point being separate from the second point;and a polishing pad strip having a first end secured to the first rollerand a second end secured to the second roller, wherein the first rollerand the second roller are configured to reciprocate so that thepolishing pad strip oscillates at least partially between the firstpoint and the second point.
 14. A chemical mechanical polishing (CMP)apparatus as recited in claim 13, further comprising: a first tensionactuator connected to the first roller and a second tension actuatorconnected to the second roller, the first and second tension actuatorsbeing configured to apply a controlled tension to the polishing padstrip.
 15. A chemical mechanical polishing (CMP) apparatus as recited inclaim 13, further comprising: a first idler roller; and a second idlerroller, the first and second idler rollers being positioned between thefirst roller and the second roller.